A better way would have been to make it explicit. i.e. "Hey X, now that we are done with business, I was wondering if you would like to meet over coffee sometime later. This will certainly not affect our professional relationship either way, but I think you're an interesting person and would like to know you better."
Some relationships though are just really dicey, like the one above. Its like having a relationship with your direct manager, since the manager is evaluating you professionally, and that's why its generally considered a bad idea.
Who knows exactly what it was like for Bill ans Melinda. It isn't difficult to pick up on social cues of someone illustrating a mutual interest in you before you outwardly hit on them. It's also not difficult to respectfully ask them if they would like to get a drink, in a personal context. There's no evidence McClure did either.
I meant it in a different way (and was being somewhat sarcastic): that in a lot of cases, office flirting (even among equal peers) can seem OK if the woman likes the guy, and creepy if they don't (e.g. he is awkward, nerdy, out of shape, etc). In essence, a comment on how "jocks" get away with more of that kind of stuff.